[Open Source] Add contributing.md (#853)

This is adapted from our `convex-backend`
[contributing.md](https://github.com/get-convex/convex-backend/blob/main/CONTRIBUTING.md)

Author: jordanhunt22

CONTRIBUTING.md

@@ -0,0 +1,28 @@
+# Contributing
+
+Please share any general questions, feature requests, or product feedback in our
+[Convex Discord Community](https://convex.dev/community). We're particularly
+excited to see what you build using Chef!
+
+Please ensure that JavaScript code is formatted with
+[eslint](https://github.com/eslint/eslint) and markdown files are
+formatted with [prettier](https://prettier.io/).
+
+Chef is a fast moving project developed by a dedicated team. We're excited to
+contribute to the community by releasing this code, but we want to manage
+expectations as well.
+
+- We value a cohesive product experience for folks building applications using Chef.
+- We value transparency in how we operate.
+
+Smaller PRs that affect documentation, comments, or small bugfixes are easy to
+review and integrate. For any larger or more fundamental changes, get in touch
+with us on Discord before you put in too much work to see if it's consistent
+with our product plans. We are generally unlikely to take large or fundamental
+changes as community contributions. We think carefully about how new features
+contribute to a cohesive product in line with our roadmap, so we cannot promise
+that larger PRs will get the same level of attention.
+
+Instructions for running Chef locally:
+
+- [Running the web app locally](DEVELOPMENT.md)